Hydraulic jarring mechanism

ABSTRACT

A bypass passage for displaced fluid in an hydraulic jarring device is equipped with a pressure responsive regulator sleeve which automatically moves axially within the fluid reservoir of the device to restrict fluid flow through the passage as required to maintain a relatively constant pressure in the compression chamber of the reservoir during an initial portion of the upstroke. An externally threaded plug is set within a threaded bore extending through the sleeve between the compression chamber and the bypass passage. The thread peaks on the plug are flattened which produces a helical orifice passage between the plug and bore which may be adjusted in length by rotating the plug which in turn establishes the high pressure value in the compression chamber. A thin wall segment supporting a portion of the plug threads moves radially in response to pressure changes to vary the cross-sectional dimensions of the orifice to assist in pressure regulation.

11 1 lltte States atent 1191 1111 3929 Roberts [451 Apr. M, T973 [54] HYDRAULIC JARRHNG MECHANISM Primary IL'.\un1im'rl)11vid H. Brown [75] Inventor: Preston C. Roberts, Terrebonc Anonwy*cmlos Torres Parish, La.

[57] ABSTRACT [73] Assignee: Kajan Specialty Co. lnc., Houma, I

La A bypass passage for dlsplaced fluid 1n an hydraulic jarring device is equipped with a pressure responsive Filedl Oct-21,1970 regulator sleeve which automatically moves axially [21] AppL 8257] within the fluid reservoir of the device to restrict fluid flow through the passage as required to maintain a relatively constant pressure in the compression [52] U.S.Cl 175/297, l75/302 Chamber of the reservoir during an initial portion of the upstroke. An externally threaded plug is set within g a threaded bore extending through the sleeve between the compression chamber and the bypass passage. The [56] References Cited thread peaks on the plug are flattened which produces a helical orifice passage between the plug and bore UNITED STATES PATENTS which may be adjusted in length by rotating the plug 3 349,858 l/l967 Chenoweth ..175/297 which in t establishes high pressure value in F 2:678,805 5/1954 Sutliff 175/302 x Compressor Chamber A thm Wan Segment l l 3,209,843 1965 Webb ..175/297 9 portion of the P threads moves radially m 3,399,741 9/1968 Monroe ...l/297 response to pressure changes to vary the cross-sec- 3,429,389 2/1969 Barrington /297 tional dimensions of the orifice to assist in pressure regulation.

19 Claims, 4 Drawing Figures v VEN TOR Preston C. Roberts ATTORNEY I Patented Apm 24,1973

2 Sheets-Sheet l l m m F a 1, m

HYDRAULIC JARRING MECHANISM BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to means for exerting a sharp, high impact force blow on an object. More specifically, the present invention relates to a new and improved hydraulic jarring mechanism for imparting a jarring blow. In a specific application, the apparatus of the present invention relates to a new and improved hydraulic jarring mechanism for use in a petroleum well for delivering a controlled, jarring blow to an object lodged in the well structure.

2. Brief Description of the Prior Art During the drilling or production of an oil or gas well, it is common for tools to become lodged in the well structure. One method generally employed to free such lodged device from the well is to latch onto the device and jar it upwardly by means of an hydraulic jar. Similar jarring forces are required for setting and retrieving a variety of tools commonly employed in oil and gas operations. In general terms, the hydraulic jar permits sudden release of a very strong tension exerted by a line extending from the wells surface to permit a sharp, jarring blow to be delivered to the lodged object.

In the typical hydraulic jar, the hydraulic fluid contained in the jar is slowly displaced from one reservoir portion to another reservoir portion, while an extremely large tension is developed through a line extending from the well surface. Metered flow of the hydraulic fluid from one portion of the reservoir to another pro vides a delay which permits extremely high tension force to be developed in the tubing or wire line. Once the jar components have moved to a certain position relative to each other, the back pressure on the hydraulic fluid is suddenly released to permit relatively unimpeded movement of the jar parts toward each other causing a hammer carried on one jar component to deliver a sharp, high intensity blow to an anvil carried on another relatively fixed jar component. The resulting blow is transmitted from the jar to the lodged compression in'the mechanism and the metering orifice for the bypass flow of the fluid. Prolonged use of such dual action sleeves eventually produces metal fatigue and wear which permits a wide variation in the extent of sleeve distension in response to the same fluid pressure particularly where the degree of distension is not confined by supporting structure.

A related shortcoming associated with employing distendable or distortable components as the sole source of regulation is that there is no simple way to vary the rate of metering orifice flow to in turn regulate the force of the jarring impact upon tripping of the tool.

SUMMARY OF THE INVENTION The hydraulic jar of the present invention is equipped with a metering bypass flow passage whichincludes provision for changing both the length and the effective cross-sectional dimensions of the flow passage. Pressure responsive means are included in the present invention to automatically maintain a preestablished, adjustable pressure within the compression chamber of the reservoir to provide a controlled jarring blow which may be uniformly repeated in each succeeding cycle.

A cylindrical hammer equipped mandrel is telescopically received within a tubular anvil equipped barrel to form an annular fluid reservoir between the two components which may be filled with an hydraulic fluid. Axially spaced, sliding seals are included between the mandrel and barrel to maintain a continuous fluid seal as the mandrel and barrel are moved axially relative to each other. The mandrel carries a seat sleeve which is adapted to engage and seal with the base of a compression sleeve as the mandrel is moved upwardly relative to the barrel. A relatively thin-walled segment is formed along the upper portion of the compression sleeve whereby the sleeve extends radially into engagement with the barrel during a first portion of its upward compression stroke which tends to increase the pressure of the hydraulic fluid.

A small amount of the compressed fluid is displaced from the compression chamber by the upwardly moving compression sleeve. The displaced fluid flows through an annular flow passage having its inlet above the advancing sleeve and its outlet below the sleeve. The flow path is defined along its inner wall by the external surface of the mandrel. The external wall of the passage includes a pressure responsive, axially movable regulator sleeve having at its upper end a sliding seal engaged against the mandrel and at its lower end a sliding seal engaged against the external surface of the seat sleeve.

The sealing areas at the upper and lower portion of the regulator sleeve are dissimilar whereby pressure variations tend to move the sleeve axially causing an in- I ternal shoulder in the sleeve to engage and disengage an external shoulder formed on the mandrel to form a variable flow restriction.

The pressurized fluid above the compression sleeve enters into the annular space between the regulator sleeve and the mandrel through an adjustable, helical orifice formed between an externally threaded plug and a radial bore set within the sleeve. The peaks of the threads on the plug are flattened to form the helical orifice which can be changed in length by changing the amount of interconnected threads between the plug and bore. An axially extending bore is formed through a portion of the plug length to provide a relatively thinwalled segment which is responsive to changes in fluid pressure causing the plug threads to move radially and therebyvary the cross-sectional dimensions of the helical orifice.

The plug and sleeve are pressure responsive to automatically establish and maintain a predetermined pressure value in the fluid being compressed by the compression sleeve. Fluid entering the helical orifice in the high pressure areas flows between the mandrel and the regulator sleeve and through vertical grooves formed between the mandrel and seat sleeve to exit in the low pressure area below the compression sleeve. The upper barrel portion includes a radially enlarged bore which disrupts the sealing engagement between the compression sleeve and the barrel wall to permit the mandrel to be moved relatively unimpeded until the mandrel hammer strikes the barrel anvil with ajarring blow. The force of the blow may be altered to any desired value by adjusting the length of the helical orifice.

It will be appreciated from the foregoing that the pressure responsive devices function automatically to maintain a predetermined pressure in the high pressure portion of the reservoir during the compression stroke of the jarring apparatus. By this means, the magnitude of the jarring blows remain consistent at any value which may be determined in advance by the positioning of the externally threaded plug.

The positioning of the metal plug within the receiving bore prevents the plug body from being distended beyond its elastic limits and thus ensures a relatively long effective lifetime. In addition, since the flow passage is varied automatically by the axial positioning of a slidable sleeve rather than by the distortion of the compression sleeve, the apparatus of the present invention is protected from damaging distortion to thereby extend the life of the device and ensure consistent functioning.

It is therefore a principal object of the present invention to provide an automatic regulating means which ensures maintenance of a constnat pressure in the reservoir of an hydraulic jar to provide a uniform, precalibrated impact force.

It is an additional object of the present invention to provide an automatically regulated flow passage which is effective in varying passage dimensions by moving components in the flow path relative to each other without distortion of the components.

It is a further object of the present invention to provide a new and improved plug type orifice meter which may be manually adjusted to vary the effective length of the orifice;

A still further object of the present invention is to provide a means for automatically varying the crosssectional dimensions of an orifice in response to the pressure of the fluid flowing through the orifice.

The foregoing and other objects, features and advantages of the present invention will be more fully understood by reference to the following specification, drawings and the appended claims.

BRIEF DESCRIPTION OFTHE DRAWINGS FIG. 1 is a partial elevation, partially in section and partially broken away, illustrating the hydraulic jarring mechanism of the present invention before the initiation ofthe compression upstroke;

FIG. 2 is a quarter section similar to FIG. I illustrating the jarring mechanism near the top ofthe upstroke;

FIG. 3 is a vertical quarter section showing the jarring mechanism at the top ofits upstroke; and

FIG. 4 is a partial section, on an enlarged scale, showing the variable orifice means of the present invcntion.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. 1, the jarring mechanism of 5 the present invention is indicated generally at 10. The

mechanism includes a mandrel 11 which is telescopically received within a tubular barrel 12. It will be understood that the upper portion of the mandrel 11 (not illustrated) is adapted to be secured to a suitable line, such as a tubing string or other suitable means, which extends from the mandrel to the well surface. The lower portion of the mandrel barrel (not illustrated) is adapted to be secured to an object which is lodged within the well structure.

The mandrel 11 and barrel 12 are radially spaced from each other to form a substantially annular reservoir 13. The upper end of the reservoir 13 is sealed by means of annular O-rings 14 which are adapted to provide a sliding seal between the barrel l2 and the mandrel 11. The lower portion of the reservoir 13 is sealed by an annular piston 15 having internal and external seal means 15a and 15b, respectively. The seal means carried by the piston 15 may be O-rings formed of rubber or other suitable material. It will be appreciated from the illustrated construction, that the piston 15 is movable axially with respect to both the mandrel 11 and the barrel 12 and functions to maintain a continuous sliding seal between the two components.

The reservoir 13 which is formed within the confines of the mandrel 11, barrel 12, seal means 14 and piston 15 is filled with a suitable hydraulic fluid which may be a high grade oil or other suitable fluid. A compression means indicated generally at 16 is disposed within the reservoir 13 and is adapted to increase the pressure of the reservoir fluid as the mandrel 11 is moved upwardly through a compression chamber 13a formed in the barrel 12.

The compression means 16 includes an annular seat sleeve 17 which is mounted within a recessed portion of the mandrel II. The sleeve 17 is prevented from moving axially with respect to the mandrel by means of a split ring 18 which is held together by a bolt 19 or other suitable means. The seat sleeve 17 is provided with an annular seat 17a which is adapted to receive a lower portion 20a of a compression sleeve 20. As more fully described hereinafter, when the mandrel 11 and attached sleeve 17 are moved upwardly with respect to the barrel 12, the compression sleeve section 20a is seated in the seat sleeve 17a in the manner illustrated in FIG. 2. An annular O-ring 17b carried in the seat sleeve 17 is adapted to engage the compression sleeve 20 to provide a leakproof fluid seal between the two mated components.

During the upward movement of the mandrel 11, seat sleeve 17 and seated compression sleeve 20, the pressure ofthe fluid above the upwardly moving sleeve 20 increases causing an upper, thin-walled section 2012 of the sleeve to distend radially outwardly into sealing engagement with the wall 12a of the compression chamber 13a. Continued upward movement of the sleeve 20 is permitted to proceed on a highly impeded basis by displacing the compressed fluid through a bypass flow passage which permits the fluid to flow downwardly through the reservoir where it exits below the compression sleeve.

With reference to FIG. 4, the initial portion of the bypass flow passage includes an adjustable length helical orifice 21 formed between an externally threaded plug 22 and an internally threaded bore 23. The peaks of the threads formed externally of the plug 22 are flattened to provide radial spacing between the flattened thread surface of the plug and the valleys in the receiving bore23. The orifice 21 thereby advances helically along the flattened thread surfaces of the body 22 and exits into a base portion 23a formed in the bore 23.

The internally threaded bore 23 is formed in a tubular regulator sleeve 24 which encircles and is axially movable with respect to the'mandrel 11. An annular, sliding seal 25 formed by a resilient O-ring or other suitable means is included along the upper portion of the regulator sleeve 24 to maintain a sliding seal between the sleeve and the mandrel. Spaced axially below the sleeve 25 is a second sliding seal 26 which is positioned at the lower end of the sleeve 24 and is designed to maintain a sliding seal between the sleeve and the upper external surface of the seat sleeve 17. A set screw 26a secures an annular metal ring 26b to the regulator sleeve 24 to maintain the O-ring and an upper metal ring 26c in proper sealing position.

The bypass flow passage of the mechanism includes the previously described helical orifice 21 and further includes a fixed radial orifice bore 23b-which extends from the base 23a of the bore 23 to a first annular passage 27 formed between the internal surface of the sleeve 24 and the external surface of the mandrel 11. The bypass is continued through a second annular passage section 28 formed between the sleeve and mandrel where it communicates across the top of the seat sleeve 17 with a plurality of axially extending, circumferentially spaced slots 170. The slots 17c extend the entire axial length of the seat sleeve 17 and exit in the low pressure portion of the rservoir below the compression means 16. From the foregoing, it may be seen the axially extending seat sleeve slots 170 where the fluid flows into the low 13. v 1

In operation, the jarring mechanism is initially in the position illustrated in F IG 1. An upwardly directed movement is imparted to the mandrel 11 through the connecting line extending to the well head causing the mandrel to move upwardly with respect to the barrel 12 which is secured to an object lodged in the well structure. The initial movement'of the mandrel and attached seat sleeve 17 engages the compression sleeve drawing the lower sleeve portion 2.0a into sealing engagement with the seal sleeve 17 in the manner previously described. As the pressure in the chamber 13a above the upwardly moving sleeve increases, the upper portion of the sleeve 20b is distended radially outwardly into a sliding sealing engagement with the wall. 12a.

The high pressure fluid above the upwardly moving compression sleeve 20 is displaced through the bypass pressure portion of the reservoir flow passage along the course previously described.

The restricted return passageway of the fluid establishes a back pressure which acts against the mandrel causing it to advance relatively slowly with respect to r the barrel 12 as substantial upward forces are developed and exerted on the mandrel from the well surface. The force required to move the mandrel through the barrel at a given rate is regulated by the length of the helical orifice 21 which may be changed.

As previously indicated, the regulator sleeve 24 is movable axially in response to fluid pressure in the reservoir to automatically vary the restriction to fluid flow as required to maintain a predetermined pressure above the advancing compression sleeve 20. The dimensions of the annular seal 25, the seal 26 and the dimensions of an internal sleeve shoulder 23c and a mandrel shoulder 11a are preferably selected so that the sleeve 24 is moved automatically in response to pressure differentials between the compression chamber and the flow passage to draw the shoulders Ila and 230 into and out of engagement to thereby vary the restriction to fluid flow through the bypass passageway.

In the preferred form, the sealing dimensions of the seal 25 are less than those of the seal 26 which in turn are less than the seating surfaces of the shoulders 11a and 230. During the initial portion of the upward stroke where fluid pressure in the compression is relatively low, the sleeve 14 is automatically forced downwardly to seat the shoulder 230 against the mandrel shoulder 11a causing a restriction to fluid flow in the bypass flow passage. When a predetermined pressure differential is developed between the increasing high pressure in the compression chamber and fluid flow passage, the regulator sleeve 24 automatically moves upwardly with respect to the mandrel to separate the two sealing shoulders. By this means, flow restriction is varied until the resultant forces acting on the sleeve 24 are equalized which produces a constant rate of fluid flow through the bypass flow passage.

When the mandrel 11 nears the upper portion of its stroke, the seal between the compression sleeve 20 and the barrel 12 is suddenly released at the point where an.

tached mandrel ll permits the mandrel to move very rapidly upwardly until a hammer 11b carried on the mandrel. strikes an anvil on the barrel to deliver the desired jarring blow. The relative positions of the components of the jarring mechanism 10 at the instant of impact are illustrated in FIG. 3. Inwardly extending barrel splines 12d mate with grooves formed, along the mandrel II to maintain the desired circumferential positioning of the two members while permitting the desired relative axial movement between the two com ponents.

After the jarring blow has been delivered, the mandrel II is lowered by releasing the tension on the line extending to the wells surface. As the mandrel moves downwardly through the barrel 12, the compression sleeve 20 moves away from the seat sleeve 17 into the relative position illustrated in FIG. 1 of the drawings. Fluid flow from the lower portion of the reservoir 13 is permitted to bypass the downwardly moving compression means 16 by flowing between the compression sleeve and the seat sleeve. An annular ring 30 equipped with teeth 30a along its upper axial end provides a flow passage between the compression sleeve and the lower portion of the regulator sleeve. When the mandrel 11 has been lowered to the beginning position, the foregoing procedure may be repeated to impart another jarring blow to the lodged object.

In addition to providing an adjustable length orifice, the plug 22 is equipped with a central bore 221) which extends along a porton of its axial length to render the plug pressure sensitive. This may best be seen by reference to FIG. 4. By means of the illustrated construction, a relatively thin-walled portion is provided in the plug 22 which is moved radially inwardly and outwardly in response to fluid pressure. The radial movement of the thin-walled portion of the plug 22 varies the spacing between the flattened portion of the plug threads and the valleys in the receiving bore 23 to alter the cross-sectional dimensions of the helical orifice 21.

From the foregoing, it may be seen that the lateral or cross-sectional dimensions of the helical orifice are automatically varied in response to pressure variations in the reservoir. It will be understood that while the plug 22 has been described as having flattened thread portions having a cross section which is substantially in the form of a truncated right triangle, the threads of the bore 23 may be flattened, if desired, to provide the helical flow passage. If the threads of both the bore 23 and the plug 22 are flattened, a dual helical orifice results.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof, and various changes in the size, shape and materials as well as in the details of the appended claims may be made without departing from the spirit ofthe invention.

What is claimed is:

1. A jarring mechanism comprising:

a. first and second relatively movable operating means connected with each other;

b. a fluid-containing reservoir included with said first and second operating means;

c. compression means connected with said first and second operating means and said reservoir means for generating and maintaining a first substantially fixed pressure in a first portion of said fluid as said first and second operating means are moved relative to each other along a first portion of their relative travel, said first pressure resisting relative movement between said first and second operating means; and

d. release means connected with said first and second operating means and said reservoir means for reducing said first pressure to a second, lower pressure when said first and second operating means are moved along a second portion of their relative travel to reduce the resistance to relative movement between said first and second operating means whereby a jarring blow is delivered between said first and second operating means;

c. said compression means including control means for automatically regulating flow ol said fluid from said first portion of said reservoir to a second portion of said reservoir for maintaining said first pressure at a substantially constant value;

f. said control means comprising variable flow passage means for automatically varying flow path dimensions in a flow passage extending between said first and second reservoir portions and including adjustable means for adjustably varying the length of said flow passage means.

2. Ajarring mechanism as defined in claim 1 wherein said adjustable means includes pressure responsive wall means forming a first portion of said flow passage means for varying the cross-sectional area of said flow passage means in response to pressure changes in said fluid.

3. Ajarring mechanism as defined in claim 2 wherein said adjustable means includes mating components comprising an externally threaded substantially cylindrical body received within an internally threaded sleeve bore with the peaks of the threads formed on at least one of saidmating components spaced from the valleys in the other of said mating components to form at least one helical flow path between said mating components. said body being rotatable within said sleeve bore for moving said body axially with respect to said bore to vary the length of said helical flow path.

4. Ajarring mechanism as defined in claim 3 wherein said pressure responsive wall means includes a bore extending axially through a threaded portion of said cylindrical body to form a tubular Wall segment whereby pressure changes in said fluid move said tubular segment radially to vary the spacing between said thread peaks and valleys in said mating components.

5. Ajarring mechanism as defined in claim 4 wherein said cylindrical body is provided with helical threads having a cross section substantially in the form of a truncated triangle.

6. Ajarring mechanism comprising:

a. first and second relatively movable operating means connected with each other; I

b. a fluid-containing reservoir included with said first and second operating means;

c. compression means connected with said first and second operating means and said reservoir means for generating and maintaining a first substantially fixed pressure in a first portion of said fluid as said first and second operating means are moved relative to each other along a first portion of their relative travel, said first pressure resisting relative movement between said first and second operating means;

d. release means connected with said first and second operating means and said reservoir means for reducing said first pressure to a second, lower pressure when said first and second operating means are moved along a second portion of their relative travel to reduce the resistance to relative movement between said first and second operating means whereby ajarring blow is delivered between said first and second operating means; and

e. control means for automatically regulating flow of said fluid from said first portion of said reservoir to a second portion of said reservoir for maintaining said first pressure at a substantially constant value, said control means including variable flow passage means for automatically varying flow path dimensions in a flow passage extending between said first and second reservoir portions;

f. said variable flow passage means including:

i. regulator sleeve means forming a second portion of said flow passage means;

ii. axially spaced first and second sliding seal means carried by said regulator sleeve means and exposed to said fluid in said first and second reservoir portions for moving said regulator sleeve means axially in response to pressure differentials between said first and second reservoir portions; and I iii. restriction forming means included with said regulator sleeve means for varying the dimensions of said flow passage means as said regulator sleeve means is moved axially. 7. A jarring mechanism as defined in claim 6 wherein said regulator sleeve means includes adjustable means for adjustably varying the length of said flow passage means.

8. Ajarring mechanism as defined in claim 7 wherein said adjustable means includes pressure responsive wall means forming a first portion of said How passage means for varying the cross-sectional area of said flow passage means in response to pressure changes in said fluid.

9. A jarring mechanism as defined in claim 6 for imparting a jarring blow to objects lodged in a well wherein:

a. said first operating means includes substantially cylindrical mandrel means adapted to be secured to and moved axially by an axially movable operating line extending to the well surface; said second operating means is adapted to be secured to an object lodged in said well and includes substantially tubular barrel means disposed about and radially spaced from a portion of said mandrel means; c. said fluid containing reservoir means includes inner and outer radial side walls formed by said mandrel means and barrel means respectively;

said reservoir means further includes axially spaced, upper and lower end wall means having sliding seal means for maintaining a leakproof seal in said reservoir means while permitting relative motion between said first and second operating means; and

e. said sliding seal means in said lower wall means of said reservoir means includes an annular piston means disposed between and axially movable with respect to said mandrel means and said barrel means.

10. A jarring mechanism as defined in claim 9 wherein said compression means includes:

a. seat sleeve means carried by said mandrel;

b. axially movable compression sleeve means disposed about and adapted to be sealingly engaged by said seat sleeve means for movement relative to said mandrel means; and

c. radially distendable sleeve means included along one end portion of said compression sleeve means for distending radially into sealing engagement with said barrel means as said mandrel means is moved relative to said barrel means.

ll. A jarring mechanism as defined in claim 10 wherein said variable flow passage means includes a flow path extending between annular shoulder means formed internally of said regulator sleeve means and annular shoulder means carried externally of said mandrel means whereby pressure induced, axial movement of said regulator sleeve means with respect to said mandrel means automatically moves said shoulder means into and out of engagement with each other to vary fluid flow between said shoulder means for maintaining said first pressure at substantially uniform value.

12. A jarring mechanism as defined in claim 11 wherein said variable flow passage means includes adjustable means for adjustably varying the length of said flow passage means.

13. A jarring mechanism as defined in claim 12 wherein said adjustable means includes pressure responsive wall means forming a first portion of said flow passage means for varying the cross-sectional area of said flow passage means in response to pressure changes in said fluid.

14. A jarring mechanism as defined in claim 13 wherein said adjustable means includes mating components comprising an externally threaded substantially cylindrical body received within an internally threaded regulator sleeve bore with the peaks of the threads formed on at least one of said mating components spaced from the valleys in the other of said mating components to form at least one helical flow path between said mating components, said body being rotatable within said sleeve bore for moving said body axially with respect to said sleeve bore to vary the length of said helical flow path.

15. A jarring mechanism as defined in claim 14 wherein said pressure responsive wall means includes a bore -extending axially through a threaded portion of said cylindrical body to form a tubular wall segment whereby pressure changes in said fluid move said tubular segment radially to vary the spacing between said thread peaks and valleys in said mating components.

16. A jarring mechanism comprising:

a. first and second relatively movable operating means connected with each other; b. a fluid-containing reservoir included with said first and second operating means;

0. compression means connected with said first and second operating means and said reservoir means for generating and maintaining a first substantially ,fixed pressure in a first portion of said fluid as said first and second operating means are moved relative to each other along a first portion of their relative travel, said first pressure resisting relative movement between said first and second operating means; and

d. release means connected with said first and second operating means and said reservoir means for reducing said first pressure to a second, lower pressure when said first and second operating means are moved along a second portion of their relative travel to reduce the resistance to relative movement between said first and second operating means whereby a jarring blow is delivered between said first and second operating means;

e. said compression means including control means for automatically regulating flow of said fluid from said first portion of said reservoir to a second portion of said reservoir for maintaining said first pressure at a substantially constant value, operation of said control means being solely dependent on differential pressure between said first and second reservoir portions.

17. A jarring mechanism as defined in claim 16 wherein said control means includes variable flow passage means for automatically varying flow path dimensions in a flow passage extending between said first and second reservoir portions.

responsive wall means forming a first portion of said flow passage means for varying the cross-sectional area of said flow passage means in response to pressure changes in said fluid. 

1. A jarring mechanism comprising: a. first and second relatively movable operating means connected with each other; b. a fluid-containing reservoir included with said first and second operating means; c. compression means connected with said first and second operating means and said reservoir means for generating and maintaining a first substantially fixed pressure in a first portion of said fluid as said first and second operating means are moved relative to each other along a first portion of their relative travel, said first pressure resisting relative movement between said first and second operating means; and d. release means connected with said first and second operating means and said reservoir means for reducing said first pressure to a second, lower pressure when said first and second operating means are moved along a second portion of their relative travel to reduce the resistance to relative movement between said first and second operating means whereby a jarring blow is delivered between said first and second operating means; e. said compression means including control means for automatically regulating flow of said fluid from said first portion of said reservoir to a second portion of said reservoir for maintaining said first pressure at a substantially constant value; f. said control means comprising variable flow passage means for automatically varying flow path dimensions in a flow passage extending between said first and second reservoir portions and including adjustable means for adjustably varying the length of said flow passage means.
 2. A jarring mechanism as defined in claim 1 wherein said adjustable means includes pressure responsive wall means forming a first portion of said flow passage means for varying the cross-sectional area of said flow passage means in response to pressure changes in said fluid.
 3. A jarring mechanism as defined in claim 2 wherein said adjustable means includes mating components comprising an externally threaded substantially cylindrical body received within an internally threaded sleeve bore with the peaks of the threads formed on at least one of said mating components spaced from the valleys in the other of said mating components to form at least one helical flow path between said mating components, said body being rotatable within said sleeve bore for moving said body axially with respect to said bore to vary the length of said helical flow path.
 4. A jarring mechanism as defined in claim 3 wherein said pressure responsive wall means includes a bore extending axially through a threaded portion of said cylindrical body to form a tubular wall segment whereby pressure changes in said fluid move said tubular segment radially to vary the spacing between said thread peaks and valleys in said mating components.
 5. A jarring mechanism as defined in claim 4 wherein said cylindrical body is provided with helical threads having a cross section substantially in the form of a truncated triangle.
 6. A jarring mechanism comprising: a. first and second relatively movable operating means connected with each other; b. a fluid-containing reservoir included with said first and second operating means; c. compression means connected with said first and second operating means and said reservoir means for generating and maintaining a first substantially fixed pressure in a first portion of said fluid as said first and second operating means are moved relative to each other along a first portion of their relative travel, said first pressure resisting relative movement between said first and second operating means; d. release means connected with said first and second operating means and said reservoir means for reducing said first pressure to a second, lower pressure when said first and second operating means are moved along a second portion of their relative travel to reduce the resistance to relative movement between said first and second operating means whereby a jarring blow is delivered between said first and second operating means; and e. control means for automatically regulating flow of said fluid from said first portion of said reservoir to a second portion of said reservoir for maintaining said first pressure at a substantially constant value, said control means including variable flow passage means for automatically varying flow path dimensions in a flow passage extending between said first and second reservoir portions; f. said variable flow passage means including: i. regulator sleeve means forming a second portion of said flow passage means; ii. axially spaced first and second sliding seal means carried by said regulator sleeve means and exposed to said fluid in said first and second reservoir portions for moving said regulator sleeve means axially in response to pressure differentials between said first and second reservoir portions; and iii. restriction forming means included with said regulator sleeve means for varying the dimensions of said flow passage means as said regulator sleeve means is moved axially.
 7. A jarring mechanism as defined in claim 6 wherein said regulator sleeve means includes adjustable means for adjustably varying the length of said flow passage means.
 8. A jarring mechanism as defined in claim 7 wherein said adjustable means includes pressure responsive wall means forming a first portion of said flow passage means for varying the cross-sectional area of said flow passage means in response to pressure changes in said fluid.
 9. A jarring mechanism as defined in claim 6 for imparting a jarring blow to objects lodged in a well wherein: a. said first operating means includes substantially cylindrical mandrel means adapted to be secured to and moved axially by an axially movable operating line extending to the well surface; b. said second operating means is adapted to be secured to an object lodged in said well and includes substantially tubular barrel means disposed about and radially spaced from a portion of said mandrel means; c. said fluid containing reservoir means includes inner and outer radial side walls formed by said mandrel means and barrel means respectively; d. said reservoir means further includes axially spaced, upper and lower end wall means having sliding seal means for maintaining a leakproof seal in said reservoir means while permitting relative motion between said first and second operating means; and e. said sliding seal means in said lower wall means of said reservoir means includes an annular piston means disposed between and axially movable with respect to said mandrel means and said barrel means.
 10. A jarring mechanism as defined in claim 9 wherein said compression means includes: a. seat sleeve means carried by said mandrel; b. axially movable compression sleeve means disposed about and adapted to be sealingly engaged by said seat sleeve means for movement relative to said mandrel means; and c. radially distendable sleeve means included along one end portion of said compression sleeve means for distending radially into sealing engagement with said barrel means as said mandrel means is moved relative to said barrel means.
 11. A jarring mechanism as defined in claim 10 wherein said variable flow passage means includes a flow path extending between annular shoulder means formed internally of said regulator sleeve means and annular shoulder means carried externally of said mandrel means whereby pressure induced, axial movement of said regulator sleeve means with respect to said mandrel means automatically moves said shoulder means into and out of engagement with each other to vary fluid flow between said shoulder means for maintaining said first pressure at substantially uniform value.
 12. A jarring mechanism as defined in claim 11 wherein said variable flow passage means includes adjustable means for adjustably varying the length of said flow passage means.
 13. A jarring mechanism as defined in claim 12 wherein said adjustable means includes pressure responsive wall means forming a first portion of said flow passage means for varying the cross-sectional area of said flow passage means in response to pressure changes in said fluid.
 14. A jarring mechanism as defined in claim 13 wherein said adjustable means includes mating components comprising an externally threaded substantially cylindrical body received within an internally threaded regulator sleeve bore with the peaks of the threads formed on at least one of said mating components spaced from the valleys in the other of said mating components to form at least one helical flow path between said mating components, said body being rotatable within said sleeve bore for moving said body axially with respect to said sleeve bore to vary the length of said helical flow path.
 15. A jarring mechanism as defined in claim 14 wherein said pressure responsive wall means includEs a bore extending axially through a threaded portion of said cylindrical body to form a tubular wall segment whereby pressure changes in said fluid move said tubular segment radially to vary the spacing between said thread peaks and valleys in said mating components.
 16. A jarring mechanism comprising: a. first and second relatively movable operating means connected with each other; b. a fluid-containing reservoir included with said first and second operating means; c. compression means connected with said first and second operating means and said reservoir means for generating and maintaining a first substantially fixed pressure in a first portion of said fluid as said first and second operating means are moved relative to each other along a first portion of their relative travel, said first pressure resisting relative movement between said first and second operating means; and d. release means connected with said first and second operating means and said reservoir means for reducing said first pressure to a second, lower pressure when said first and second operating means are moved along a second portion of their relative travel to reduce the resistance to relative movement between said first and second operating means whereby a jarring blow is delivered between said first and second operating means; e. said compression means including control means for automatically regulating flow of said fluid from said first portion of said reservoir to a second portion of said reservoir for maintaining said first pressure at a substantially constant value, operation of said control means being solely dependent on differential pressure between said first and second reservoir portions.
 17. A jarring mechanism as defined in claim 16 wherein said control means includes variable flow passage means for automatically varying flow path dimensions in a flow passage extending between said first and second reservoir portions.
 18. A jarring mechanism as defined in claim 17 wherein said variable flow passage means includes adjustable means for adjustably varying the length of said flow passage means.
 19. A jarring mechanism as defined in claim 18 wherein said adjustable means includes pressure responsive wall means forming a first portion of said flow passage means for varying the cross-sectional area of said flow passage means in response to pressure changes in said fluid. 